Use observations to explain random particle motion and diffusion.通过观察，解释粒子的随机运动和扩散。
| English | 中文 |
|---|---|
| particle | 粒子 |
| random motion | 随机运动 |
| diffusion | 扩散 |
| atom | 原子 |
| molecule | 分子 |
| ion | 离子 |
Try each question before opening its hint or answer. Use paper for calculations and diagrams.先独立尝试，再展开提示或答案。计算和画图可以在纸上完成。
A smell spreads through a room. Does this mean every smell particle moves away from the source?
Distinguish the motion of an individual particle from the overall change in concentration.区分单个粒子的运动方向与浓度的整体变化。
No. Each particle moves randomly. Overall, more particles move from the concentrated region into less concentrated regions than in the reverse direction.不是。每个粒子都随机运动。整体而言，从高浓度区域进入低浓度区域的粒子比反向移动的更多。
A drop of dye spreads through still water. Explain why stirring is not necessary.
Consider the motion of dye and water particles.考虑染料粒子和水分子的运动。
Particles move continuously and randomly. This leads to a net spreading of dye from higher to lower concentration without stirring.粒子持续随机运动，使染料整体从高浓度区域扩散到低浓度区域，即使没有搅拌也会混合。
A student says diffusion stops when the colour becomes uniform. Correct the statement.
Separate individual motion from net movement.区分粒子的持续运动与整体的净移动。
Particles continue moving randomly. Once concentration is uniform, there is no overall movement down a concentration gradient.粒子仍在随机运动。浓度均匀后，不再有沿浓度梯度的整体净移动。
For more written practice, use Lesson 1 in your worksheet.